Inside the heart, there are four main valves providing one-way blood flow. Tricuspid and mitral separates the atria from the ventricles, respectively, the right and left, while lunate (pulmonary and aortic) separate the ventricles from the large arteries. All four valves are attached to the fibrous skeleton of the heart.
It consists of dense connective tissue and serves as a support for the valves and muscles of the heart. The surface of the valves and the inner surface of the chambers of the heart are lined with a single layer of endothelial cells. The myocardium is the thickest layer consisting of muscle cells.
The epicardium is the outer layer of the heart, another name for the visceral pericardium, which, together with the parietal pericardium, forms the fibrous-serous sac – the heart sac.
The superior and inferior vena cava, the coronary sinus flow into the right atrium, blood returns from the systemic veins and coronary arteries. The tricuspid valve is located at the bottom of the atrium and opens into the cavity of the right ventricle.
The right ventricle has papillary muscles, with the help of tendon threads attached to the valves of the tricuspid valve, the pulmonary valve is located at the outlet of the right ventricle, through which blood enters the pulmonary artery. Four pulmonary veins flow into the left atrium. The mitral valve opens into the left ventricle.
The thickness of the left ventricle is an average of 11 mm, which is three times thicker than the wall of the right ventricle. The left ventricle has two papillary muscles, tendon filaments are connected with two cusps of the mitral valve. The aortic valve separates the left ventricle from the aorta, has three cusps attached to the fibrous ring.
Right above the valve leaflets, the right and left coronary arteries originate. Atrial septum – separates the left and right atria, interventricular – the right and left ventricle consists of muscle and membrane parts. Venous blood enters the heart through the inferior and superior vena cava, which flows into the right atrium.
Then the blood, through the tricuspid valve, enters the right ventricle. When the right ventricle contracts, blood through the valve of the pulmonary artery enters the pulmonary artery and lungs, where gas exchange occurs; blood loses carbon dioxide and is saturated with oxygen.
Blood enriched with oxygen returns to the heart through the pulmonary veins into the left atrium and then, passing through the mitral valve, enters the left ventricle.
When the left ventricle contracts, oxygen-enriched blood enters the aorta through the aortic valve, and then it is delivered to all organs and tissues of the body. Fibrous rings isolate the atrial muscle fibers from the muscle fibers of the ventricles, so that excitation can be carried out through a special conduction system of the heart.
The main components of the cardiac conduction system include the sinoatrial node, the atrioventricular node, the bundle of His, the right and left legs of the bundle of His, and Purkinje fibers.
A significant portion of the right leg of the His bundle passes through the moderator bundle. The cardiac conduction system consists of specialized cells that initiate heartbeat and coordinate the contraction of the heart chambers.
From the SU in the atria, an electrical impulse, that is, excitation, propagates along the conducting paths: the front – Bachmann (connects the right and left atria), the middle – Wenckebach – to the upper-posterior part of the atrioventricular (AV) node.
The longer Torel rear tract is pumped at the lower edge of the AV node. Ashof-Tavar’s antioventricular node is located at the base of the right atrium in the interatrial septum, its length consists of 5 – 6 mm. Blood supply has in 80% – 90% of cases of PKA.
Location and Anatomy
In the chest, a large volume is occupied by the heart. It is not located exactly in the center, two-thirds are located to the left of the midline, and only a small part is to the right.
The shape is elongated, but may vary in people of different ages, physique, changes in the presence of diseases.
The pericardial bag affects how a person’s heart looks. If fluid accumulates inside it, the organ takes on the shape of a ball.
In the heart, there are:
- The top. This part is directed to the left and down, formed in most of the left ventricle.
- The base, which is located higher and to the right, it is formed by the atria.
- The anteroposterior and posterior lower surfaces are separated by the right and left edges of the heart.
The size of the heart can fluctuate in people with different physical fitness, body weight. The weight of the body is approximately 320 g, in athletes this figure increases due to muscle mass, with obesity, fat tissue predominates. An organ consists of several layers. Each has a different structure, performs its functions.
- The endocardium lines the cavities from the ins >
The heart, cor, is an almost conical hollow organ with well-developed muscle walls. It is located in the lower part of the anterior mediastinum on the tendon center of the diaphragm, between the right and left pleural sacs, enclosed in a pericardium, pericardium, and fixed by large blood vessels.
The heart has a shorter rounded, sometimes more elongated, sharp shape; in a filled state in size, it approximately corresponds to the fist of the person under study. The dimensions of the heart of an adult are individual. So, its length reaches 12-15 cm, the width (transverse size) is 8-11 cm, and the anteroposterior size (thickness) is 6-8 cm.
The mass of the heart varies from 220 to 300 g, and in people involved in sports, it is 400-450 g. In men, the size and weight of the heart is larger than in women, and its walls are somewhat thicker.
The posterior upper dilated part of the heart is called the base of the heart, basis cordis, large veins open into it and large arteries exit from it. The frontal free part of the heart is called the apex of the heart, apes cordis. Of the two surfaces of the heart, the lower, flattened, diaphragmatic surface, facies diaphragmatica (inferior), is adjacent to the diaphragm.
The anterior, more convex sternum-costal surface, facies sternocostalis (anterior), faces the sternum and costal cartilage. Surfaces pass one into another with rounded edges, while the right edge (surface), margo dexter, is longer and sharper, the left pulmonary (lateral) surface, facies pulmonalis, is shorter and rounded.
Three grooves are distinguished on the surface of the heart. The coronary sulcus, sulcus coronarius, is located on the border between the atria and ventricles. The anterior and posterior interventricular sulci, sulci interventriculares anterior et posterior, separate one ventricle from the other.
On the sternocostal surface, the coronal groove reaches the edges of the pulmonary trunk. The place of transition of the anterior interventricular sulcus to the posterior corresponds to a small depression – notch of the apex of the heart, incisura apicis cordis. In the furrows lie the vessels of the heart.
When an adult is calm, the heart contracts approximately in the range of 70-80 cycles per minute. One beat of the pulse equals one heart cycle. At this rate of contraction, one cycle takes about 0,8 seconds.
Of which the atrial contraction time is 0,1 seconds, the ventricles are 0,3 seconds and the relaxation period is 0,4 seconds. The cycle frequency is set by the heart rate driver (the part of the heart muscle in which the pulses occur that regulate the heart rate). The following concepts are distinguished:
- Systole (contraction) – almost always under this concept is the contraction of the ventricles of the heart, which leads to a push of blood along the arterial bed and maximization of pressure in the arteries.
- Diastole (pause) – the period when the heart muscle is in a state of relaxation. At this point, the chambers of the heart are filled with blood and the pressure in the arteries decreases.
So when measuring blood pressure, two indicators are always recorded. As an example, let’s take the numbers 110/70, what do they mean?
- 110 is the upper number (systolic pressure), the blood pressure in the arteries at the time of the heartbeat.
- 70 is the lower number (diastolic pressure), the blood pressure in the arteries at the time of relaxation of the heart.
A simple description of the heart cycle:
- At the moment of relaxation, the hearts, atria, and ventricles (through open valves) are filled with blood.
- Atrial systole (contraction) occurs, which allows you to completely move the blood from the atria to the ventricles.
Atrial contraction begins from the place where the veins flow into it, which guarantees the primary compression of their mouths and the inability of blood to flow back into the veins.
Conventionally, for one beat of the pulse there are two heart contractions (two systoles) – atria are first reduced, and then the ventricles. In addition to ventricular systole, there is atrial systole. Atrial contraction is not worthwhile with measured heart function, since in this case the relaxation time (diastole) is enough to fill the ventricles with blood.
However, once the heart begins to beat more often, the atrial systole becomes crucial – without it, the ventricles simply would not have time to fill up with blood. The blood flow through the arteries is carried out only with the contraction of the ventricles, it is these tremors that are called the pulse.
Cavities and valves
Of the cavities of the heart, only the main parts of the atria have a smooth wall. In the ears (parts of the atria), and especially in the ventricles, fleshy protrusions (trabeculae carneae) protrude into the internal cavity.
All cavities are lined with a single-layer epithelium (endocardium). Four heart valves are fixed by rings of dense fibrous connective tissue in such a way that they lie in a plane. Together with the septum of the connective tissue, they form a cardiac skeleton, to which atria and ventricles are attached from above and below.
Valve valves between the atria and ventricles are formed by a double layer of the endocardium. The free ends of the valves are attached to the papillary muscles by the tendon chords and (chordae tendineae).
Tendon chords prevent the valves from turning in the direction of the atria, preventing the reverse flow of blood during the contraction of the ventricle. Between the right atrium and the right ventricle is a valve with three valves (tricuspid valve). The left ventricle from the left atrium is separated by a valve with two valves (bicuspid, mitral valve).
At the entrance to the pulmonary artery and aorta, lunar valves are located. They prevent backflow during ventricular contraction. Semilunar valves consist of three pockets of the double layer of the epicardium, which open into the lumen of the vessel with their outer surface facing the heart.
When the pockets of the lunar valve are filled with blood, the valve is closed. With increasing blood pressure in the ventricle, the pockets are pressed against the walls of the vessel, and the valve opens.
The heart consists of cavities, or chambers. Two smaller ones are called the atria, two large chambers are the ventricles. The atrial septum separates the right and left atria. The right and left ventricle are separated from each other by the interventricular septum.
As a result, venous and aortic blood is not mixed inside the heart. Each of the atria communicates with the corresponding ventricle, but the opening between them has a valve. The valve between the right atrium and ventricle is called a tricuspid, or tricuspid, because it consists of three valves.
The valve between the left atrium and ventricle consists of two cusps. Atrial ventricular valves provide unidirectional blood flow from the atrium to the ventricle. Blood from the whole body, rich in carbon dioxide (venous), is collected in large vessels: the superior and inferior vena cava.
Their mouths open in the wall of the right atrium. From this chamber, blood flows into the cavity of the right ventricle. The pulmonary trunk delivers blood to the lungs, where it becomes arterial. Through the pulmonary veins, it goes into the left atrium, and from there into the left ventricle.
From the latter begins the aorta – the largest vessel in the human body, through which blood enters the smaller and enters the body. The pulmonary trunk and aorta are separated from the ventricles by the corresponding valves that prevent retrograde (reverse) blood flow.
The heart muscle (myocardium) is the bulk of the heart. The myocardium has a complex layered structure. The thickness of the wall of the heart varies from 6 to 11 mm in its various departments. Conducting system of the heart is located in the depth of the heart wall. It is formed by a special fabric that generates and conducts electrical impulses.
Electrical signals excite the heart muscle, causing it to contract. In the conducting system there are large formations of the nervous tissue: nodes. The sinus node is located in the upper part of the myocardium of the right atrium. It produces impulses responsible for the work of the heart.
In the lower segment of the atrial septum is the atrioventricular node. The so-called bundle of His departs from it, dividing into right and left legs, which break up into increasingly smaller branches.
The smallest branches of the conductive system are called “Purkinje fibers” and are directly in contact with muscle cells in the wall of the ventricles. The chambers of the heart are lined with endocardium. Its folds form the heart valves, which we talked about above.
The outer membrane of the heart is the pericardium, which consists of two leaves: parietal (external) and visceral (internal). The visceral layer of the pericardium is called the epicardium. In the gap between the outer and inner layers (leaves) of the pericardium, there are about 15 ml of serous fluid, which ensures their sliding relative to each other.
The right atrium is located in the area of the right side of the base of the heart, has the shape of an irregular cube, the apex of which forms the right atrial ear directed forward. In the right atrium, the following walls can be distinguished:
- external, which is facing to the right,
- internal, which is directed to the left and is common to the right and left atria,
- interatrial septum,
- top, back and front walls.
The bottom wall is missing; here is the right atrioventricular foramen communicating the right atrium with the right ventricle. The right ear, the most protruding part of the atrium, has the appearance of a flattened cone directed by the apex to the left, towards the pulmonary trunk.
With its inner curved surface, the ear is directed to the aortic root. Outside, the upper and lower edges of the ear have small irregularities. Two – the upper and lower – the vena cava, the coronary sinus and the small own veins of the heart flow into the right atrium.
The superior vena cava collects blood from the head, neck, upper limbs and body walls and opens at the border of the upper and anterior walls of the right atrium with the opening of the superior vena cava.
The inferior vena cava collects blood from the lower extremities, walls and organs of the pelvic and abdominal cavities; it opens at the border of the upper and posterior walls of the right atrium with an opening of the inferior vena cava.
On the front edge of the mouth of the inferior vena cava from the side of the atrial cavity there is a lunate-shaped muscle flap of the inferior vena cava, which goes to it from the oval fossa, the atrial septum. This damper in the fetus directs blood from the inferior vena cava through the oval opening into the cavity of the left atrium.
The shutter often contains one large outer and several small tendon threads. Both vena cava form an obtuse angle; the distance between their mouths reaches 1,5–2 cm. The coronary sinus is the common collector of the heart’s own veins. The confluence of the coronary sinus is located on the border between the medial and posterior wall of the right atrium.
The smallest veins of the heart include the smallest veins of the heart that collect blood from its walls. They open with several holes of the smallest veins, mainly on the septum dividing the atria, and on the lower parts of the right and front walls of the atrium. The relief of the inner surface of the right atrium varies. The inner (left) and back walls are smooth.
The outer (right) and front surfaces are uneven due to the fact that crest muscles protrude into the atrial cavity in the form of ridges, among which the upper and lower muscle bundles are distinguished: the upper follows from the mouth of the vena cava to the upper wall of the atrium, the lower is directed along the lower border of the right wall up from the coronal sulcus.
On the relatively smooth inner (left) wall of the right atrium, i.e., the septum between the atria, there is a flat recess, the oval fossa is an overgrown oval hole that communicates between the right and left atrial cavities in the embryonic period.
The bottom of the oval fossa is very thin, and in adults it quite often has a slit-like shape, the size of a pinhead, the hole is the rest of the oval hole in the heart of the fetus, clearly distinguishable from the left atrium.
The right ventricle of the anterior and posterior interventricular grooves is delimited on the surface of the heart from the left ventricle; coronary groove separates it from the right atrium. The outer (right) edge of the right ventricle is pointed and is called the right edge.
The right ventricle has the shape of an irregular triangular pyramid, the base of which is directed up towards the right atrium, the apex is down and to the left. The front wall of the right ventricle is convex, the posterior is flattened. The left, inner, wall of the right ventricle is the interventricular septum, it is concave from the side of the left ventricle, that is, it projects towards the right ventricle.
On the cross section at the level of the apex of the heart, the cavity of the right ventricle represents an anteriorly posterior fissure, and at the border of the upper and middle third it is the shape of a triangle, the basis of which is a partition between the ventricles protruding into the cavity of the right ventricle.
In the cavity of the right ventricle, two departments are distinguished: a wider posterior, actually the cavity of the ventricle, and a narrower anterior. The posterior part of the ventricular cavity through the right atrioventricular opening, which is located on the right and behind, communicates with the cavity of the right atrium.
The described hole from the right atrium has an oblong-rounded shape. The anterior part of the ventricular cavity, the arterial cone (funnel), has a cylindrical shape and smooth walls. From the side of the outer surface it is convex.
Its cavity, with the help of the opening of the pulmonary trunk, passes upward into the pulmonary trunk. Between the posterior and anterior sections of the right ventricle there is a well-defined muscle shaft – the supraventricular crest, going arched from the atrioventricular opening to the area of the arterial cone.
The right atrial ventricular valve, a tricuspid valve, which prevents the return of blood from the cavity of the right ventricle to the cavity of the right atrium, formed by the duplicate of the inner lining of the heart – endocardium, is attached around the circumference of the same hole.
In the thickness of the valve there is a small amount of connective, elastic tissue and muscle fibers; the latter are associated with the muscles of the atrium. The tricuspid valve is formed by three triangular-shaped leaflets (lobes-teeth): septum leaf, posterior leaflet, anterior leaflet, all three leaflets with their free edges protrude into the cavity of the right ventricle.
Of the three cusps, one large, septal, cusp is located closer to the septum of the ventricles and attaches to the medial part of the right atrioventricular opening. A smaller sash is attached to the posterior periphery of the same opening.
The anterior valve, the smallest of all three valves, is strengthened at the anterior periphery of the same opening and faces the arterial cone. Often between the septum and the posterior cusps, a small additional tooth can be located.
The free edges of the leaflets have small notches. With their free edges, the valves are turned into the cavity of the ventricle. Thin tendon strings, which usually begin from the papillary muscles, are attached to the edges of the cusps, and some of the threads are fixed to the cusp surface facing the ventricular cavity.
Tendon strings of three papillary muscles are attached to three cusps of the tricuspid valve so that each of the muscles is connected with its two threads to two adjacent cusps. Three papillary muscles are distinguished in the right ventricle.
One, permanent, large papillary muscle, the tendon filaments of which are attached to the posterior and anterior folds; this muscle moves away from the anterior wall of the ventricle – the anterior papillary muscle. Two others, insignificant in size, are located in the area of the septum – the septal papillary muscle (not always available), and the posterior wall of the ventricle – the posterior papillary muscle.
The opening of the pulmonary trunk, located in front and on the left, leads to the pulmonary trunk, three semilunar valves formed by the endocardial duplication are attached to its edge: the front, right and left, their free edges protrude into the pulmonary trunk. All three of these valves together form the valve of the pulmonary trunk.
The left atrium, like the right atrium, has an irregular cuboid shape, but with thinner walls than the right. It distinguishes between the upper, front, rear and outer (left) walls. The inner (right) wall is the interatrial septum. The bottom wall is the base of the left ventricle.
In the posterior section of the upper atrial wall, four openings of the pulmonary veins open, bringing arterial blood from the lungs to the cavity of the left atrium. In this case, the mouths of both right, as well as both left, pulmonary veins lie very close to one another, while between the mouths of the right and left veins there is a space corresponding to the upper posterior portion of the wall of the left atrium.
The lower wall of the left atrium is pierced by the left atrioventricular opening, through which the cavity of the left atrium communicates with the cavity of the left ventricle. The inner surface of the left atrium is smooth, with the exception of the inner (right) wall and abalone.
The inner (right) wall of the left atrium, representing, as said, the atrial septum, has a flat recess corresponding to an oval fossa; it is bordered by a fold – a flap of the oval hole (crescent septum), which represents the remainder of the flap of the oval hole that existed in the embryonic period.
The inner surface of the left abalone has numerous crested muscles intertwined in different directions.
The left ventricle in relation to other parts of the heart is located to the left, back and down. It has an oblong-oval shape. The narrowed anteroposterior part of the left ventricle corresponds to the apex of the heart. The border between the left and right ventricles on the surface of the heart corresponds to the anterior and posterior interventricular grooves (heart).
The outer (left) edge of the left ventricle has a rounded shape and is called the pulmonary surface. The cavity of the left ventricle is longer and narrower than the cavity of the right ventricle. On a cross section, the cavity of the left ventricle at the apex of the heart represents a narrow gap, which approaches the oval shape closer to the base.
In the cavity of the left ventricle, two departments are distinguished: a wider posterior one, representing its own cavity of the left ventricle, and a narrower anterior right one, which is a continuation of the cavity of the left ventricle.
The posterior part of the cavity of the left ventricle communicates with the cavity of the left atrium using the left atrial ventricular opening, which is located to the left and back. It is smaller than the right atrioventricular opening and has a more rounded shape.
The antero-right part of the cavity of the left ventricle communicates with the aorta through the aortic opening. Around the circumference of the left atrioventricular opening, the left atrioventricular (mitral) valve is attached, the free edges of its valves protrude into the cavity of the ventricle.
They, like the tricuspid valve, are formed by doubling the inner layer of the heart, endocardium. This valve, when the left ventricle contracts, prevents the passage of blood from its cavity back into the cavity of the left atrium.
The valve distinguishes between the front cusp and the rear cusp, in the intervals between which two small teeth are sometimes located. The anterior cusp, hardening on the front sections of the circumference of the left atrioventricular opening, as well as on the closest connective tissue base of the aortic opening, is located to the right and more anteriorly than the posterior.
The free edges of the anterior cusp are fixed by tendon strings to the anterior papillary muscle, which starts from the anteroposterior wall of the ventricle. The front wing is slightly larger than the rear. Due to the fact that it occupies the area between the left atrioventricular opening and the aortic opening, its free edges are adjacent to the aortic orifice.
The rear wing is attached to the back of the circumference of the specified hole. It is smaller than the front one and is located somewhat posteriorly and to the left with respect to the hole. Through tendon chords, it is fixed mainly to the posterior papillary muscle, which begins on the posterior wall of the ventricle.
Small teeth, lying in between large ones, are fixed with tendon filaments either to the papillary muscles or directly to the wall of the ventricle. In the thickness of the teeth of the mitral valve, as in the thickness of the teeth of the tricuspid valve, there are connective tissue, elastic fibers and a small amount of muscle fibers associated with the muscle layer of the left atrium.
The anterior and posterior papillary muscles can each be divided into several papillary muscles. From the septum of the ventricles, as in the right ventricle, they begin very rarely. From the side of the inner surface, the wall of the posterolateral part of the left ventricle is covered with a large number of protrusions – fleshy beams.
Splitting repeatedly and reconnecting, these fleshy beams are intertwined and form a network that is denser than in the right ventricle; there are especially many of them at the apex of the heart in the area of the interventricular septum.
Three ailunar valves of the aorta are attached around the circumference of the aortic opening, which, according to their position in the opening, are called right, left, and posterior lunar valves. All together form an aortic valve.
Semilunar valves of the aorta are formed, like the semilunar valves of the pulmonary trunk, by endocardial duplication, but are more developed. The aortic valve nodule embedded in the thickness of each of them is more thickened and solid.
Physiology of cardiac activity
The main function of the heart is contractile. This organ is a kind of pump, providing a constant flow of blood through the vessels. Cardiac cycle – repeated periods of contraction (systole) and relaxation (diastole) of the heart muscle.
Systole provides an ejection of blood from the heart chambers. During diastole, the energy potential of the heart cells is restored. During systole, the left ventricle ejects about 50 – 70 ml of blood into the aorta. The heart pumps 4 to 5 liters of blood per minute.
Under load, this volume can reach 30 liters or more. Atrial contraction is accompanied by an increase in pressure in them, while the mouths of the hollow veins flowing into them are closed. Blood from the atria is squeezed into the ventricles.
Then comes the diastole of the atria, the pressure in them drops, while the cusps of the tricuspid and mitral valves close. Ventricular contraction begins, resulting in blood flowing into the pulmonary trunk and aorta.
When systole ends, the pressure in the ventricles decreases, the valves of the pulmonary trunk and aorta are closed. This ensures unidirectional movement of blood throughout the heart. With valve defects, endocarditis and other pathological conditions, the valve apparatus cannot ensure the tightness of the heart chambers.
Blood begins to flow retrograde, disrupting myocardial contractility. The contractility of the heart is ensured by electrical impulses that occur in the sinus node. These impulses arise without external influence, that is, automatically.
Then they are conducted along the conducting system and excite muscle cells, causing them to contract. The heart also has intracretory activity. It releases biologically active substances into the blood, in particular, atrial natriuretic peptide, which promotes the release of water and sodium ions through the kidneys.
The mass of the heart of an adult and the norm of the frequency of contractions. The size of the heart of a healthy person correlates with the size of his body, and also depends on the intensity of physical activity and metabolism.
The approximate heart weight in women is 250 g, in men – 300 g. That is, the average adult heart weight is 0,5% of body weight, while at the same time the heart consumes about 25-30 ml of oxygen (09) per minute at rest – about 10% of total consumption 09 alone.
With intense muscle activity, consumption of 02 heart increases 3-4 times. Depending on the load, the coefficient of performance (COP) of the heart is from 15 to 40%. Recall that the efficiency of a modern diesel locomotive reaches 14-15%. Blood flows from the high pressure area to the low pressure area.
The heart adapts to the constantly changing conditions of a person’s life: daily routine, physical activity, food, ecology, stressful situations, etc. At rest, the ventricles of an adult push about 5 liters of blood into the vascular system per minute.
This indicator – minute volume of blood circulation (IOC) – with heavy physical work increases by 5-6 times. The ratio between the IOC at rest and with the most intense muscle work speaks of the functional reserves of the heart, and therefore, the functional reserves of health.
What is the heart for? As you already understood, the heart produces uninterrupted blood flow throughout the body. Three hundred grams of muscle, elastic and mobile, is a constantly working suction and delivery pump, the right half of which absorbs the blood used in the body from the veins and directs it into the lungs for oxygen enrichment.
Then, blood from the lungs enters the left half of the heart and, with a certain degree of effort, as measured by the level of blood pressure, ejects blood. Blood circulation during blood circulation occurs approximately 100 thousand times a day, at a distance of over 100 thousand kilometers (this is the total length of the vessels of the human body).
Over the year, the number of heart contractions reaches an astronomical value of 34 million. During this time, 3 million liters of blood are pumped. Gigantic work! What amazing reserves are hidden in this biological engine!
It’s interesting to know: enough energy is spent on one reduction to lift a load weighing 400 g to a height of one meter. Moreover, a calm heart uses only 15% of all the energy that it has. With hard work, this figure increases to 35%.
Unlike skeletal muscle muscles, which can remain at rest for hours, myocardial contractile cells work tirelessly for many years. This raises one important requirement: their air supply must be uninterrupted and optimal.
If there are no nutrients and oxygen, the cell dies instantly. She cannot stop and wait for delayed doses of life-giving gas and glucose, since she does not create the reserves necessary for the so-called maneuver. Her life is to take a sip of fresh blood.
The cardiac conduction system is a group of special formations consisting of non-standard muscle fibers (conducting cardiomyocytes), which serve as a mechanism for ensuring the coordinated work of the heart departments.
The path of passage of the impulse This system provides automaticity of the heart – the excitation of impulses that are born in cardiomyocytes without an external stimulus. In a healthy heart, the main source of impulses is the sinoatrial (sinus) node. He is the leader and blocks impulses from all other pacemakers.
But if there is any disease leading to a sick sinus syndrome, then other parts of the heart take on its function. So the atrioventricular node (automatic center of the second order) and the bundle of His (AC of the third order) are able to activate when the sinus node is weak.
There are cases when secondary nodes enhance their own automatism during normal operation of the sinus node. The sinus node is located in the upper posterior wall of the right atrium in the immediate vicinity of the mouth of the superior vena cava. This node initiates pulses with a frequency of approximately 80-100 times per minute.
The atrioventricular node (AB) is located in the lower part of the right atrium in the atrioventricular septum. This septum prevents the spread of the impulse directly into the ventricles, bypassing the AV node.
If the sinus node is weakened, the atrioventricular will take over its function and begin to transmit impulses to the heart muscle with a frequency of 40-60 contractions per minute. Next, the atrioventricular node passes into the His bundle (the atrioventricular bundle is divided into two legs).
The right leg rushes to the right ventricle. The left leg is divided into two more halves. The situation with the left leg of the bundle of His is not fully understood. It is believed that the left leg fibers of the anterior branch rush to the front and side walls of the left ventricle, and the posterior branch supplies the fibers to the posterior wall of the left ventricle, and the lower parts of the side wall.
In case of weakness of the sinus node and atrioventricular block, the His bundle is able to create impulses at a speed of 30-40 per minute. The conducting system deepens and further branches into smaller branches, eventually turning into Purkinje fibers, which penetrate the entire myocardium and serve as a transmission mechanism for contracting the muscles of the ventricles.
Purkinje fibers are able to initiate pulses with a frequency of 15-20 per minute. Exceptionally trained athletes can have a normal heart rate at rest up to the lowest recorded number – only 28 heart contractions per minute!
However, for the average person, even if he leads a very active lifestyle, a pulse rate below 50 beats per minute can be a sign of bradycardia. If you have such a low heart rate, you should be examined by a cardiologist.
Heart rate, tones
The heart rate in a newborn is 120 beats per minute. With aging, the average person’s pulse stabilizes between 60 and 100 beats per minute. Well-trained athletes (we are talking about people with a well-trained cardiovascular and respiratory systems) have a pulse of 40 to 100 beats per minute.
The nervous system controls the rhythm of the heart – the sympathetic strengthens the contractions, and the parasympathetic weakens. Cardiac activity, to a certain extent, depends on the content of calcium and potassium ions in the blood. Other biologically active substances also contribute to the regulation of heart rhythm.
Our heart can begin to beat more often under the influence of endorphins and hormones secreted when listening to your favorite music or kiss. The endocrine system can have a significant effect on heart rate – and on the frequency of contractions and their strength.
For example, the adrenal secretion of well-known adrenaline causes an increase in heart rate. The hormone opposite in effect is acetylcholine.
One of the simplest methods for diagnosing heart disease is to listen to the chest with a stethophonendoscope (auscultation). In a healthy heart, during a standard auscultation, only two heart sounds are heard – they are called S1 and S2:
- S1 – the sound is heard when the atrioventricular (mitral and tricuspid) valves are closed during ventricular systole (contraction).
- S2 – the sound is heard when closing the lunate (aortic and pulmonary) valves during diastole (relaxation) of the ventricles.
Each sound consists of two components, but for the human ear they merge into one due to the very short time interval between them. If, under normal auscultation conditions, additional tones are heard, then this may indicate some kind of disease of the cardiovascular system.
Sometimes additional abnormal sounds called heart murmurs may be heard in the heart. As a rule, the presence of noise indicates any pathology of the heart.
For example, noise can cause blood to return in the opposite direction (regurgitation) due to improper operation or damage to a valve. However, noise is not always a symptom of a disease. To clarify the causes of the appearance of additional sounds in the heart, it is worth doing an echocardiography (ultrasound of the heart).
The circulatory system
The cardiovascular system in humans is formed by two circles of blood circulation. With every heartbeat, blood moves immediately in both circles. Small circle of blood circulation.
- Deoxygenated blood from the superior and inferior vena cava enters the right atrium and then into the right ventricle.
- From the right ventricle, blood is pushed into the pulmonary trunk. The pulmonary arteries conduct blood directly to the lungs (to the pulmonary capillaries), where it receives oxygen and gives off carbon dioxide.
- Having received enough oxygen, the blood returns to the left atrium of the heart by pulmonary veins.
Big circle of blood circulation.
- From the left atrium, the blood moves into the left ventricle, from where it is subsequently pumped through the aorta into the pulmonary circulation.
- Having passed a difficult path, blood through the vena cava again arrives in the right atrium of the heart.
Normally, the amount of blood expelled from the ventricles of the heart is the same with each contraction. So in the big and small circles blood circulation simultaneously receives an equal volume of blood.
What is the difference between veins and arteries?
- The veins are designed to transport blood to the heart, and the task of the arteries is to deliver blood in the opposite direction.
- In veins, blood pressure is lower than in arteries. Accordingly, in arteries, the walls are characterized by greater extensibility and density.
- Arteries saturate the “fresh” tissue, and the veins take the “spent” blood.
- In case of vascular damage, distinguish arterial or venous bleeding can be distinguished by its intensity and blood color.
Arterial – a strong, pulsating, beating “fountain”, the color of blood is bright. Venous – bleeding of constant intensity (continuous flow), the color of blood is dark.
The simplest and most affordable method for examining the heart is electrocardiography (ECG). Using it, you can determine the frequency of heart contraction, identify the type of arrhythmia. It is also possible to detect ECG changes in myocardial infarction. Only by the result of ECG the diagnosis is not made.
For confirmation, other laboratory and instrumental methods are used. For example, in order to confirm the diagnosis of myocardial infarction, in addition to an ECG study, you need to take blood to determine troponins and creatine kinase.
The most informative in terms of visualization is an ultrasound scan (ultrasound) of the heart. On the monitor screen, all the structures of the heart are clearly visible: both the atria, and the ventricles, and the valves, and the vessels of the heart.
An ultrasound scan is especially important if there are complaints: weakness, shortness of breath, prolonged increase in body temperature, a feeling of palpitations, interruptions in the work of the heart, pain in the heart, moments of loss of consciousness, swelling on the legs. And also in the presence of:
- changes in electrocardiographic examination;
- heart murmur;
- high blood pressure;
- any form of coronary heart disease;
- pericardial disease;
- systemic diseases (rheumatism, systemic lupus erythematosus, scleroderma);
- congenital or acquired heart defects;
- lung diseases (chronic bronchitis, pneumosclerosis, bronchiectasis, bronchial asthma).
The high information content of this method allows you to confirm or exclude heart disease. Laboratory blood tests are usually used to detect myocardial infarction, heart infections (endocarditis, myocarditis).
When examining for the detection of heart diseases, they most often examine:
- C-reactive protein,
- creatine kinase – MV,
- lactate dehydrogenase (LDH),
- white blood cell count
- cholesterol and triglycer >
Now cardiovascular diseases are attacking people at an active pace, especially the elderly. Millions of deaths per year – such is the outcome of heart disease. This means: three out of five patients die directly from heart attacks. Statistics note two alarming facts: the growing trend of diseases and their rejuvenation.
Heart diseases include 3 groups of diseases that affect:
- Valves of the heart (congenital or acquired heart defects);
- Heart vessels;
- Tissues of the shells of the heart.
This is a disease that affects the blood vessels. With atherosclerosis, complete or partial closure of blood vessels occurs, which also affects the work of the heart.
This disease is the most common disease associated with the heart. The inner walls of the vessels of the heart have a surface covered with calcareous deposits, compacting and narrowing the lumen of the life-giving channels (in Latin “heart attack” means “locked”).
For the myocardium, vascular elasticity is very important, since a person lives in a wide variety of motor modes.
For example, you take a leisurely stroll, looking at shop windows, and suddenly remember that you need to be early at home, the bus you need arrives at the bus stop, and you rush forward to catch it. As a result of this, the heart begins to “run” with you, dramatically changing the pace of work.
The vessels that feed the myocardium, in this case, expand – the nutrition should correspond to increased energy consumption. But in a patient with atherosclerosis, the lime plastering the vessels, as it turns the heart into a stone – it does not respond to his desires, since he is not able to miss as much working blood to feed the myocardium as it needs when running.
This happens with a car, the speed of which cannot be increased if clogged pipelines do not supply a sufficient amount of “gasoline” to the combustion chambers.
This term refers to a disease in which a complex of disorders occurs due to a decrease in myocardial contractility, which is a consequence of the development of stagnant processes.
With heart failure, blood stagnation occurs in both the small and large circles of blood circulation.
With heart defects, defects in the valve apparatus can be observed, which can lead to heart failure. Heart defects can be either congenital or acquired.
This pathology of the heart is caused by a violation of the rhythm, frequency and sequence of the heartbeat. Arrhythmia can lead to a number of disorders of the heart.
With angina pectoris, oxygen starvation of the heart muscle occurs.
This is one of the types of coronary heart disease, in which there is an absolute or relative insufficiency of blood supply to the myocardial site.
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